This invention relates to the application of x-radiation to a subject and, more particularly, to a modulation of an x-ray beam with a microwave signal to produce in the subject radiation at a microwave frequency to be absorbed by pathological material including macromolecules, such as oncogenes, for treatment of malignancy.
Microwave radiation and x-rays have each been employed in medical procedures for destroying malignant material, particularly body tissue afflicted with various forms of cancer. Energy of the radiation is absorbed by the material with a resultant change in the physical and the chemical properties of the material, this resulting in a termination of the malignancy. The biological material to be treated by the radiation may be formed of desoxyribonucleic acid, the genetic material of which the chromosomes of human cells are composed. The desoxyribonucleic acid consists of pairs of macromolecules containing a backbone of units of five carbon atoms linked by phosphorous and oxygen atoms, each unit having a side chain of a purine or pyramidine base. Viruses and genes that cause cancer (oncogenes) consist of such macromolecules, and have lengths on the order of 4,000 or more bases, or a backbone of some 20,000 atoms.
In order to understand the interaction of the microwave radiation with the macromolecules, it is useful to consider some basic concepts in the energy levels of electrons of the various atoms arranged in the macromolecules. In accordance with electrostatic theory, the potential energy of an electron is inversely proportional to the distance of the electron from the nucleus of the atom, the distance defining an equipotential surface. The electric field, or attractive force between the nucleus and the electron, is given by the gradient of the potential surface and, accordingly, varies with the inverse square of the distance. A transfer of an electron from one of the allowable quantum energy levels to a second energy level is accomplished by the expenditure or absorption of an amount of energy equal to the difference of potential between the two levels. In terms of mathematics, apart from a proportionality constant, the energy values of the two levels are given by (1/a) and (1/b) wherein a and b are the distances between the nucleus and the energy level. This is a simplistic model assuming spherical energy levels. During a transition of energy state, wherein an electron moves from one potential level to the other potential level, the change in energy is proportional to (1/a-1/b) which is equal to (b-a)/ab. This being equal to d/ab wherein d is the difference between a and b, and is understood to be very much smaller than either a or b. Therefore, the energy expended in a transition of electrons between two potential levels is proportional to the distance between the two potential levels. The amount of energy to totally remove an electron from an atom is equal to the energy of the potential level, which, as noted above, is inversely proportional to the radius of the potential surface.
Interaction of a beam of radiation with molecules of material is characterized by a transfer of energy from the beam to an electron in an atom of a molecule. The energy in a photon of the beam is proportional to the frequency of the radiation, the proportionality factor being the Plank constant. In the situation wherein the energy of the photon is equal to the transition energy required to elevate an electron from an inner energy level to an outer energy level, the transfer of energy occurs readily with extinction of the photon. In this situation, the frequency of the radiation has a value, which may be referred to as the resonant frequency, which provides the photon with the requisite energy for accomplishing the transition in electron energy state.
The foregoing analysis has been based on a simplistic model in which each of the atoms of the molecule is provided with spherically shaped electron energy levels. In actuality, the electron energy levels among the thousands of atoms in macromolecules, at least in the outer energy levels, are altered both in physical shape and in energy level. This results in numerous energy levels which characterize the specific macromolecule and the material composed of the macromolecules. The lowest energy transitions for electrons in single atoms result in absorption of radiation in the spectrum of visible light, this radiation having a frequency of approximately 2.times.10 exp (14) Hertz (Hz). The frequency of radiation for absorption at the lowest transition energy of molecular energy levels varies inversely with the size of the molecule. A molecule of 20,000 atoms in length would be expected to absorb radiation at a frequency of approximately 1/20,000 that of light, namely, a frequency of 10 exp (10) Hz, this being in the microwave range and having a wavelength of three centimeters.
A problem exists with presently available equipment and methodology for the administration of microwave radiation to subject matter, for removing a malignancy by way of example, in that the microwave radiation has minimal penetration. X-ray, on the other hand, is transmitted throughout the subject relatively non-selectively, rather than being directed to specific regions of interest. The specific regions embedded within the subject require the radiation therapy while the remaining portion of the subject does not require such therapy. While it may be possible to illuminate the subject from different directions so as to concentrate the dosage at limited absorption, the specific regions, relatively large doses are required because of limited absorption, and a significant amount of radiation is absorbed by the remainder of the subject. This reduces the radiation available for the specific regions, and may interfere with the functioning of the remaining portion of the subject.